Listen to Robert Emmerich introduce "The Big Apple," a hit song from 1937. Music written by Bob and performed by Tommy Dorsey's Clambake Seven with Bob on piano. Lyrics written by Buddy Bernier and sung by Edythe Wright. Audio provided by Dorothy Emmerich.

"Red equals green” (or “red means green") is a professional wrestling adage meaning that blood ("red") attracts professional wrestling fans and makes money ("green"). The saying “red equals green” has been cited in print since at least 1999, although the “red means green” adage appears to have been known in the professional wrestling business of the 1970s and 1980s.

The infamous 1985 (not 1983, as cited in the glossary below) ABC “20/20” television segment by John Stossel about professional wrestling (Stossel was injured by a wrestler during an interview at Madison Square Garden) popularized the “red means green” term.

PWTorch.com Glossary
Red Means Green (phrase): A old phrase used to point out that wrestlers who bled would often get a bigger payoff from a promoter if he was willing to blade [dfn.] and bleed. Term made famous when it was featured on the 1983 ABC “20/20” story by John Stossell exposing the inner workings of pro wrestling.

21 February 1985, The Oregonian (Portland, OR), “Wrestler hits ‘20/20’ reporter” by Ed Bark (Dallas Morning News), pg. D8, col. 4:
(ABC 20/20 consumer reporter John Stossel—ed.)
“But they can’t rehearse the whole match. So only the end moves are planned. The rest they ad lib, and during the headlocks they plan the next moves. We also mention how they sometimes cut themselves on the forehead with razor blades to make themselves bleed. And Mansfield does that for the camera. They don’t use blood capsules. They use real blood. The promoter tells them, ‘All right, you’re gonna bleed tonight.’ They have an expression: ‘Red means green.’”

New York (NY) Times
TV NOTES; ABC REPORTER MAY SUE WRESTLER WHO HIT HIM
By PETER W. KAPLAN
Published: February 23, 1985
John Stossel, a reporter for ABC’s ‘’20/20’’ magazine program, says he may sue the professional wrestler named ‘’Dr. D.’’ The blond, bearded wrestler, who is 6 feet, 6 inches tall and weighs 268 pounds, hit Mr. Stossel on both sides of the head, leaving him, Mr. Stossel says, with possible permanent pain and buzzing in his ears.
(...)
Mr. Stossel interviewed the wrestler on Dec. 28 at Madison Square Garden. In a ‘’20/20’’ segment that was broadcast Thursday night, Mr. Stossel attempted to show that professional wrestling was a monopoly and that bouts were, in the words of one former wrestler on the program, ‘’predetermined.’’

Google Groups: alt.pro-wrestling.wwf
James D
Jul 6 1999
I think when they bleed from the forehead that it is real. There was a news expose on wrestling in the mid eighties on how they did this. They have a razor blade hidden. It only takes a small slice and you will get a lot of blood in the forehead region. I believe the saying back then was ‘red equals green.’

TSM ForumsnotJames
Mar 22 2002, 01:58 PM
(...)
Nowadays, I know to look for the guy to take the “blading position”, but back then, it was pretty intense to see the blood. Of course, today, “red equals green” so…

Google BooksWrestling at the Chase:
The inside story of Sam Muchnick and the legends of professional wrestling
By Larry Matysik
Toronto: ECW Press
2005
Pg. 208:
Brody agreed with promoters who argued “red means green.” Blood could draw at the box office.

The Intelligent Monster
Friday, December 24, 2010
Covers that Kick Ass and Chew Bubble Gum; 1st in a series
(...)
It wasn’t just comic book covers that separated me from my money as a kid. I loved professional wrestling as a kid (and still do, at least from that 1970’s-80’s period) so I was often as likely to come home with a wrestling mag as I was a comic book. They were always bombastic and often bloody like the cover above; its a popular notion in wrestling that “red equals green”, that the bloodier the cover was the higher it sold.

Columbia News Service
March 11, 2011
‘Blading’ Wrestlers Bleed Green
By Daniel Johnson
(...)
Blading is also known as gigging, juicing and drawing color, says Sean Oliver, the owner of Kayfabe Commentaries, a video production company that shoots behind-the-scenes interviews with wrestlers. As Alvarez says, whatever someone calls it, “red equals green” for wrestling promoters: They use blood to make money.